A conventional flow meter 1, such as Taiwan patent No. M285697 disclosed, referring to FIGS. 1 and 2, the flow meter 1 includes a hollow flow tube 2 and an indication meter 3 installed on an outer side of the flow tube 2. The flow tube 2 is connected to a pipe P for various types of liquid to flow, and includes with a conical seat 21, a movable spring sleeve 22 and a magnetic ring 23 that are installed therein. The conical seat 21 includes at least one aperture 211 and an extension 212 formed at a conical shape and extended from one side thereof. The movable spring sleeve 22 includes an inner annular surface 221 formed therein which includes an opening 220 run through by the extension 212, and an inner slot 222 formed therein opposing the conical seat 21 for accommodating the magnetic ring 23. The movable spring sleeve 22 has one end opposing the conical seat 21 to press a spring 24 against the inner side of the flow tube 2. The indication meter 3 includes a pointer 32 with a magnetic member 31 mounted thereon and a scale plate 33 corresponding to the pointer 32.
The flow meter 1, through liquid W in the flow tube 2 flowing through the aperture 211 of the conical seat 21, generates a pressure to push the movable spring sleeve 22 to move. Therefore, the mutual magnetic attraction between the magnetic ring 23 and magnetic element 31 will drive the pointer 32 to swivel, and the flow flux of the liquid W can be measured. However, the indication meter 3 is installed on the outer side of the flow tube 2 and requires an installation space. It is easily being blocked and masked in situations where a lot of pipes P are installed near the flow meter 1. Such situation produce inconvenience for operation people to check the indication meter 3. Besides, the indication meter 3 is used to monitor and measure the flow flux of the liquid W onsite. In practice, when the flow flux of the liquid W shown on the indication meter 3 is over a limit range flow of the liquid W has to be stopped. For setting the flow flux limitation, the indication meter 3 has to be detached to adjust the pointer 32 or the magnetic element 31, or be replaced by other detection meters to meet the required functions. Hence, aside from taking extra space and being blocked easily, the indication meter 3 of the conventional flow meter 1 also has disadvantages that it requires detachment for setting flow monitoring and cannot replace the scale plate 33 of different precisions immediately.